Structural and magnetic properties of exchange-spring FeTaN/FeSm/FeTaN multilayers

The structural and magnetic properties of FeTaN/FeSm/FeTaN multilayers, deposited by dc magnetron sputtering, have been investigated as function of the alloy layers thickness. Structural and morphological characterizations, accomplished by transmission electron microscopy, X-ray reflectivity and grazing-incidence X-ray diffraction, account for a well-defined layered structure of the multilayers with a limited interface roughness. The magnetization reversal process is examined experimentally using magneto-optical Kerr vector magnetometry by measuring the longitudinal and transverse hysteresis loops. It is found that, for soft layer thickness above 3.2 nm, the magnetization reversal occurs via the formation of a stable exchange-spring state in which the magnetic moments of the outermost soft layer gradually rotates away from the unswitched underlying hard layer.